The present invention relates to new water-soluble polypeptides, DNA sequences, new cells, the preparation process of said polypeptides, their use as medicaments and the compositions containing them.
xcex1 and xcex2 interferons form a group of secreted proteins endowed with diverse biological properties and characterized by their ability to induce, in the cells of vertebrates, an antiviral and anti-proliferative state (I. Gresser and M. G. Tovey, Biochem. Biophys. Acta 516:23/1978).
xcex1 interferon has significant effects on the immune, cellular and humoral system, in particular on the polyclonal activation of B cells (M. Peters, J. Immunol., 137:3153/1986), the inhibition of the T cell functions (J. Knop et al, J. Immunol., 133:2412/1984) and the modification of the expression of histocompatibility antigens (M. Fellous et al, Eur. J. Immunol., 9:446/1979). All these processes are involved in the development of auto-immunity.
Although interferon is considered as a beneficial factor for the organism, an abnormal production of interferon may contribute to the pathology of certain illnesses and in fact is associated with various so-called auto-immune illnesses. For example, high levels of interferon are present in the serum or tissues of patients suffering from various illnesses, such as lupus erythematosus, rheumatoid arthritis, Behcet""s syndrome, diabetes mellitus, multiple sclerosis, aplasia of the marrow and a serious multiple immuno-deficiency illness. A direct correlation exists between the levels of this interferon and the poor prognosis of the development of the AIDS illness (E. Buimovivi-Klein et al; AIDS Res., 2:99/1986).
It has been shown that in a specific mouse strain (NZB) suffering from a spontaneous illness, which illness serves as an animal model of lupus erythematosus in man, the administration of xcex1 or xcex2 interferon aggravates the progression of the illness (H. Heremans et al, Infect. immun., 21:925/1978; C. Adam et al, Clin. Exp. Immunol., 40:373/1980).
In young mice, the administration of large quantities of interferon induces a growth-inhibition syndrome, necrosis of the liver and death (I. Gresser et al, Nature, 258:76/1975). Also, infection by certain viruses (such as the viruses of Pichinde lymphocytic choriomeningitis, or rheovirus) during the neonatal period of the female mouse is accompanied by the production of large quantities of endogenic interferon which brings about the same lethal syndrome. The administration of an xcex1 or xcex2 anti-interferon antibody protects the young mice infected at birth by the viruses of this syndrome mentioned above (Y. Riviere et al, Proc. Natl. Acad. Sci. USA, 74:2135/1977; Y. Riviere et al, J. Exp. Med., 152:633/1980; T. Clark et al, J. Virol, 59:728/1986). This experiment represents a convincing argument for the harmful role of interferon in the pathogenesis of this illness.
Furthermore, the activation of NK cells and the modification of the expression of histocompatibility antigens are both regulated by xcex1 or xcex2 interferon and play an important role in the rejection of bone marrow grafts (C. Ohien et al, Science, 246:66/1989). In fact, it was demonstrated that the production of xcex1 or xcex2 interferon is one of the essential elements in the resistance of F1 hybrid mice to a graft of the parental marrow (Afifi et al, J. Immunol., 134:3739/1985). Thus the treatment of F1 mice or also of allogenic mice by a murine xcex1 or xcex2 anti-interferon serum allows the grafting and proliferation of the parental or allogenic marrow (Afifi et al, 1985).
It is also known that the biological effects of interferons and their sub-types are generated by their interaction with a specific receptor which has a high affinity for the cell surface (M. Aguet et K. E. Mogensen, Academic Press, London, 1983).
At present no effective therapy exists for auto-immune illnesses and for other illnesses such as multiple sclerosis, which is suspected of having a connection with auto-immune illnesses. The present treatments for auto-immune type illnesses are unsatisfactory and have toxic effects. Those used in xe2x80x9canti-rejectionxe2x80x9d therapies inhibit the manifestations of these pathologies but not their causes and have a very high toxicity. It would therefore be highly desirable to have available medicaments having therapeutic effects and a reduced toxicity for auto-immune illnesses and organ rejections.
It would therefore be very desirable to block the action of (xcex1 or xcex2) interferon by injection of an antagonist which in this way could be therapeutically beneficial for auto-immune type illnesses and for preventing the rejection of grafts. However, such an approach based on the injection of foreign immunoglobulin which has proved its effectiveness is not practical in a therapeutic treatment in man.
That is why the present Application relates to a new approach which is based on the use of a soluble form of the specific receptor of xcex1 interferon as antagonist to block the action of xcex1 or xcex2 interferon. These variants of the natural receptor, prepared by genetic engineering techniques, retain the ability to fix the endogenic xcex1 interferon either circulating or locally, and are deprived of the part which fixes them to the cell surface; they can circulate freely and due to their specificity only link up with xcex1 or xcex2 interferon.
By fixing xcex1 or xcex2 interferon, they are capable of blockingxe2x80x94as an antibody wouldxe2x80x94the action of xcex1 or xcex2 interferon in the organism.
It would therefore be desirable to have available a product capable of blocking the activity of xcex1 and/or xcex2 interferon.
That is why a subject of the present Application is a water-soluble polypeptide, characterized in that it has a high affinity for xcex1 and xcex2 interferons.
By xe2x80x9chigh affinityxe2x80x9d is meant a dissociation constant of less than 10xe2x88x929 M.
By xe2x80x9cwater-solublexe2x80x9d is meant that the said polypeptide is capable of circulating ,in an organism such as the human body then of fixing itself to a cell.
In the present Application, and in what follows, by xe2x80x9chybridxe2x80x9d is meant the product resulting from the fusion (or conjugation) of a water-soluble polypeptide according to the present invention (xe2x80x9csolublexe2x80x9d part of the natural receptor, modified complete receptor, or xe2x80x9csolublexe2x80x9d part of the natural receptor modified for example by substitution) and of another molecule, in particular of polypeptide type, such as an immunoglobulin or an immunoglobulin fragment.
By xe2x80x9csoluble receptor of xcex1 and xcex2 interferonsxe2x80x9d (or of interferon) is meant one of the water-soluble polypeptides as defined above.
In order to simplify the wording, in what follows, xe2x80x9cinterferon receptorxe2x80x9d will generally be referred to instead of xe2x80x9creceptor for xcex1 and xcex2 interferonsxe2x80x9d.
Among the polypeptides as defined above, a particular subject of the invention is a water-soluble polypeptide, characterized in that it corresponds to the formula given in annex 1.
This polypeptide corresponds to the extra-cellular soluble part of the natural native receptor of xcex1 or xcex2 interferon.
Of course polypeptides other than the polypeptide described above retain a high affinity for the said interferons. It is thus that the polypeptide given in annex 1 could be replaced in particular by substitution or deletion variants which are also part of the subject of the present Application.
With regard to the deletions, one or more amino acids of the polypeptide corresponding to FIGS. 1A-1B could be suppressed without unfavourably modifying the affinity vis-à-vis the xcex1 and xcex2 interferons.
Deletions could also relate to the complete and native receptor, in particular at the level of its soluble part, in such a way for example as to make it lose its ability to fix itself to the cell membrane and therefore make it available in the circulation.
If one starts with the sequence of the native and complete receptor of interferon given in annex 2, the trans-membrane and cytoplasmic sections of its sequence could for example be suppressed.
The deletion of the 437-457 residues corresponding to the trans-membrane region and the 458-557 residues (cytoplasmic region) will for example be carried out to obtain the soluble forms (circulatory).
The complete sequence of amino acids and nucleotides, coding for the complete receptor of xcex1 and xcex2 interferons is represented in annex 2.
In the case where deletions are carried out in the trans-membrane and cytoplasmic (or cellular and intra-cellular) sections, potentially immune epitopes can be avoided. One advantage of the native receptor xcex1 and xcex2 interferons whose trans-membrane region has been suppressed is its ability to be secreted in the supernatant of the culture medium of the recombinant host cells.
Therefore a subject of the present Application is water-soluble polypeptides, characterized in that they result from deletion of polypeptides corresponding to the formula of annex 1 or annex 2.
The substitution variants are also part of the subject of the present Application.
In this case, one or more amino acids in the sequence of the interferon receptor could be removed or replaced by others, the total number of amino acids being retained.
The substitutions will preferably relate to the soluble part of the interferon receptor. The substantial changes in the function or the immunological identity of the soluble part of the receptor will be carried out by selecting non-conservative substitutions as well as residues of amino acids or sequences which differ from those present originally on the polypeptide in a way which is most significant as regards their property of maintaining the three-dimensional structure of the polypeptide close to the substitution, of maintaining the conjugate or hydrophobicity of the molecule or most of the side chain.
The substitutions modifying most of the properties of the receptor are in particular
those in which an amino acid residue, for example seryl or threonyl, is substituted by a hydrophobic residue, for example leucyl, isoleucyl, phenylalanyl, alanyl or valyl;
those in which a cysteinyl is replaced by any residue;
those in which a residue having an electropositive side chain, such as lysyl, arginyl or histidinyl residues, is replaced by an electronegative residue, for example glutamyl or aspartyl;
and those in which a residue having a bulky side chain, for example phenylalanyl, is replaced by a residue which does not have one.
The substitution variants may also relate to the structure of the complete interferon receptor and will relate in particular to its trans-membrane region. In fact, the substitutions at this level, by reducing the affinity of the said polypeptide for lipid cells or membranes, will produce a soluble form of the receptor of xcex1 and xcex2 interferons.
The trans-membrane section could be for example substituted by a different amino acid sequence, for example a homopoly-nucleotide DNA sequence or any sequence containing 5 to 50 identical amino acids, for example serine, lysine, arginine, glutamine and aspartic acid or other hydrophilic amino acids permitting the secretion of soluble receptors into the culture medium of the recombinant host cells.
Therefore a subject of the present Application is also water-soluble polypeptides, characterized in that they result from substitution of the pqlypeptides corresponding to the formula of annex 1 or annex 2.
The above information shows that both substitutions or deletions as well as combinations of such modifications could be carried out.
In a general way, the variants thus obtained will have no functional trans-membrane section and preferably will have no intra-cellular (cytoplasmic) part.
Other variants of the water-soluble polypeptides described above could be produced by chemical modification, in order in particular to improve the characteristics of the receptor of xcex1 and xcex2 interferons.
Such polypeptides could contain hydrophilic polymers such as polyethyleneglycol grafted onto their amino acids containing free amino groups such as lysine, or sulfhydryl groups such as cysteine.
These modifications could in particular give the polypeptides according to the present invention a higher half-life in plasma or also an increase in their solubility or finally a reduction of the immunogenic nature of the said polypeptides.
These modifications can be carried out by well-known methods such as for example those described in the U.S. Pat. No. 4,179,337.
A subject of the present Application is also the polypeptides described above, characterized in that they are hydridized (or also conjugated).
The conjugation can involve immuno-competent polypeptides, for example polypeptides which can cause an immune response in an animal to which the hybrid polypeptide is administered or which can link up with any antibody directed against the part of the polypeptide which does not correspond to the soluble interferon receptor.
In a general way, the epitopes which do not correspond to the said receptor will contain antigens recognized by the already-existing antibodies, for example polypeptide fragments of bacteria, such as betagalactosidase.
Immune conjugations can be carried out by cross-linking in vitro or by recombinant cell culture transformed by a DNA coding for an immunogenic polypeptide.
In the preferred conditions, the immunogenic agent will be inserted into or linked to the soluble receptor or a fragment derived from the soluble receptor by a polypeptide bond so as to obtain a linear polypeptide chain containing epitopes corresponding to the soluble receptor and at least one epitope foreign to the said receptor. These epitopes can be introduced into any other locus in the polypeptide chain compatible with the receptor or its fragments.
Such hybrids can be particularly useful when a formulation containing a pharmacologically acceptable support is administered to an animal with a view to the preparation of an antibody against the interferon receptor; these antibodies are themselves useful as diagnostic agents or for the purification of the native receptor or the soluble receptor of interferon.
Other conjugated polypeptides which can be immunogenic contain hybrids containing in addition to the water-soluble polypeptide that has been conjugated with the C-terminal region of a polypeptide according to the invention, a homopolymer such as a pentahistidine. The hybrid could then be easily isolated by using chelating agents such as zinc ions fixed to a support thus permitting the adsorption of the hybrid from impure mixtures and its elution. The soluble receptor can then be recovered for example by enzymatic cleavage.
Other hybrids can be produced to improve the secretion of the soluble receptor. A heterologous signal polypeptide replaces that of the soluble receptor and if the resultant hybrid is recognized by the host cell, it is used by the host cell and the receptor is secreted.
The selection of signal polypeptides can be carried out on the basis of the characteristics of the host cell used and can include sequences of bacteria, yeasts, fungi, plants, mammals or viruses.
In the preferred conditions, the polypeptides described above are conjugated with polypeptides, in particular possessing a structure adapted for slowing down their degradation in the human organism.
The hybridization in particular of plasma proteins having a plasma half-life greater than that of the soluble part of the receptor itself (usually greater than 20 hours for these plasma proteins) with a soluble polypeptide according to the present invention will permit the duration of action of the soluble polypeptide to be extended.
Such plasma proteins contain for example serum-albumin, apolipoproteins, transferrins and preferably immunoglobulins, in particular G type, and especially G1 type.
Preferably, such hybrids will not be immunogenic in the animal or man for whom they will be used and the said plasma proteins will also not bring about harmful side effects in patients due to their own habitual biological activity.
In the preferred implementation conditions, the water-soluble polypeptide according to the invention will be conjugated with an immunoglobulin, in particular at the level of its constant region. A preferred immunoglobulin will be of G type, in particular G1 type.
The immunoglobulins and some of their variants are known; many were prepared by recombinant cell culture (Kohler et al, PNAS, USA, 77, 2197 (1980); Morrison et al, Ann. Rev. Immunol. 2, 239 (1984)).
The polypeptides according to the present invention which have the activity of the extra-cellular part of the native receptor of xcex1 and xcex2 interferons can be conjugated by their C-terminal end to the N-terminal end of the constant region of the light chain or the heavy chain.
In this way the variable region can be replaced and at least the CH2 and CH3 transition region of the constant region of the heavy chain is retained in a functionally-active form.
For this the appropriate DNA sequence can be constructed and expressed in the recombinant culture cells.
The immunoglobulins and the other polypeptides having in particular a half-life in the plasma greater than that of the soluble receptor of the xcex1 and xcex2 interferons can be conjugated with the said receptor and with its variants according to the same process.
The extra-cellular part of the interferon receptor will contain at most 427 to 436 amino acids starting from the initial methionine (see annex 1).
Generally, the sequences containing the cell region including the fixation region will be conjugated with the sequence of the immunoglobulins.
The precise conjugation site is not critical. The boundaries indicated above are only to be considered as indications and other neighbouring sites for the soluble interferon receptor can be chosen with the aim of optimizing the secretion or the fixation characteristics of the soluble receptor of the xcex1 and xcex2 interferons. The optimum site could be determined by the usual experiments.
In general, it has been found that the hybrids are expressed in the cell, but with some variation in the degree of secretion of the recombinant host cells. The following table shows different immunoglobulinxe2x80x94interferon receptor fusions which were obtained:
(a) RCl
(b) (RCl)2
(c) (RCh)2
(d) (RCl)2(RCh)2
in which xe2x80x9cRxe2x80x9d represents a part of the extra-cellular section of the soluble receptor of and interferons containing the fixation site and Cl and Ch represent the constant areas of the light chain and the heavy chain respectively of human immunoglobulin. The above structures represent the main structures only, for example they do not show the joint (J) region or other sections of the immunoglobulin, or the disulphide bridges. When such sections are necessary for binding activity, they must be present in the position that they occupy naturally in the soluble receptor of xcex1 and xcex2 interferons, immuno-receptor of xcex1 and xcex2 interferons or immunoglobulin.
These examples are representative for bifunctional hetero-antibodies containing different ligand-receptor sites where a VhCh immunoglobulin will be able to be linked with a predetermined antigen. More complex structures will result when using heavy chains of immunoglobulins of other classes, for example IgM, IgG2, 3, 4, IgA, IgE, IgD, but preferably IgG1.
A preferred hybrid results from the fusion of the N-terminal end of the soluble receptor of xcex1 and xcex2 interferons which contains the fixation site for the ligand of xcex1 and xcex2 interferons in the C-terminal part Fc of an antibody which contains the functions effecting immunoglobulin G1. Such examples are illustrated hereafter in the experimental part.
Such hybrids contain typically the first 436 amino acids or the first 427 amino acids of the soluble receptor of xcex1 and xcex2 interferons linked by their C-terminal end to the constant region of the K chain or the G1 chain. The DNA coding for the soluble receptor of xcex1 and xcex2 interferons described in annex 1 is synthesized by using a combination of the PCR reaction (Polymerase Chain Reaction: see R. K. Saiki et al, Science 239, 487-491 (1988)) and digestions by appropriate restriction enzymes as illustrated in the examples.
Complementary oligonucleotides were used in the cDNA sequence at the 5xe2x80x2 end and at the predetermined sites downstream of the cDNA of the (a/b) IFN receptor on the basis of the sequence shown in annex 2.
As the template for the PCR reaction, a plasmid was used containing complete cDNA (Uzxc3xa9 et al) or a lambda bacteriophage. A commercially-available cDNA library can also be used; the cDNA fragment can also be synthesized directly from total RNA or from polyA+ RNA prepared according to well-known methods (see O. Ohara et al, PNAS 86, 5673-77 (1989), J. Delort et al, Nucl. Acid Res. 17, 6439-6448 (1989)). The CDNA or RNA library can be obtained from human cells such as Daudi, Namalwa or from organs such as the human spleen with essentially the same result.
The interferon receptor appears to be a unique polypeptide. Its sequence nevertheless has a certain allelic variation.
The DNA fragment is inserted into the DNA coding for the constant region of the light or heavy chain of an immunoglobulin; the latter will preferably be a human immunoglobulin if the fusion is intended for therapeutic treatments in man.
DNAs which code for immunoglobulins are known, can be obtained commercially or can be synthesized (see for example Adams et al, Biochemistry 19, 2711-2719 (1980); Gough et al, Biochemistry 19, 2702-2710 (1980); Dolby et al, PNAS USA 77, 6027-6031 (1980); Rice et al, PNAS USA 79, 7862-7865 (1982); Falkner et al, Nature 298, 286-288 (1982) and Morrison et al, Ann. Rev. Immunol. 2, 239-256 (1984)).
The DNAs which code for the hybrids will preferably be transfected into the host cells with a view to their expression.
If the host already produces heavy immunoglobulin chains before transfection, it is then sufficient to transfect the soluble receptor hybrid of light chain xcex1 and xcex2 interferons, in order to produce a bifunctional hetero-antibody. Similarly, if the host cell already expresses a light chain, then the DNA which codes for the soluble receptor hybrid of heavy chain xcex1 and xcex2 interferons can be transfected in order to produce a bifunctional antibody. The bifunctional immunoglobulins which contain one or more chains containing is the fixation site of the xcex1 and xcex2 interferons and one or more chains containing variable regions are endowed with double specificity, namely vis-à-vis xcex1 and xcex2 interferons and vis-a-vis a predetermined antigen. These are produced by the processes mentioned above or by processes in vitro. In the latter case, for example, F(ab)2 fragments of the hybrid are prepared according to known methods (see for example the U.S. Pat. No. 4,444,878).
An alternative for producing bifunctional antibodies consists of fusing B cells or hybridomas which secrete antibodies having the specificity for a desired antigen with cells which produce hybrids of the soluble receptor for immunoglobulin xcex1 and xcex2 interferons, for example myelomas. The bifunctional antibodies can be recovered from culture supernatants of such hybridomas.
A subject of the present Application is DNA sequences, characterized in that they code for the water-soluble polypeptides described above or their hybrids in particular with polypeptides.
Examples of polypeptides having a high affinity for xcex1 and xcex2 beta interferons of mammals are for example the soluble receptors of xcex1 and xcex2 interferons of primates, the soluble receptors of human, murine, canine, feline, bovine, equine and porcine xcex1 and xcex2 interferons. These DNA sequences which code for these polypeptides have a certain number of uses. More particularly, these sequences or parts of sequences or their synthetic or semi-synthetic copies can be used to screen other cDNA libraries or human or animal genomic libraries to select by hybridization other DNA sequences which are similar to the soluble receptor ofxcex1 and xcex2 interferons. Such DNAs, their fragments or their synthetic or semi-synthetic copies represent variants of the soluble receptors of xcex1 and xcex2 interferons and can be used as the starting material for preparing other variants by mutation. Such mutations cannot change the sequence of amino acids coded by the mutated codons or on the contrary change the amino acids. The two types of mutations can be advantageous for the production or use of the soluble receptor of xcex1 and xcex2 interferons according to the present invention. These mutations can for example permit a high-level production, a simpler purification or a higher binding activity.
As an example of a DNA sequence, the sequence of the nucleotides from 1-1343 of annex 2 can be mentioned.
The DNA coding for the variants of the natural soluble receptor of xcex1 and xcex2 interferons will preferably be presented in a form which permits it to be expressed in a transcription unit under the control of control elements for transcription and translation of mammals, of micro-organisms or of viruses compatible with the envisaged host cell. After transformation, transfection or infection of appropriate cells, such vectors can permit the expression of the recombinant polypeptide. The variants of the natural soluble receptor of xcex1 and xcex2 interferons can be expressed in cells of mammals, yeasts, bacteria or other cells under the control of an appropriate promoter. Cloning and expression vectors for use with hosts of bacteria, fungi, yeasts or mammal cells are described by Pouwels et al, (Cloning Vectors: A laboratory manual, Elsevier, N.Y., 1985) the relevant parts of which are mentioned here by way of reference. The expression vector can, but does not have to, carry a replication site as well as one or more sequences of selection markers which permit selection in transformed cells.
The variations introduced into the DNA coding for the polypeptides described above must not change the reading frame and must not create complementary sequences which could produce secondary structures harmful to the expression.
The polypeptide variants of the natural soluble receptor of interferon will have approximately the same binding activity as the natural receptor, although it is possible to select the variants with a view to changing the characteristics of the receptor, for example in order to improve them, as indicated above.
Although the mutation site is fixed, the mutation itself is not. For example, to optimize the performance of a mutation at a given site, the codon or target region could be mutated at random and the polypeptide variants obtained screened with a view to finding the optimum combination of secondary activities. The techniques for introducing substitution mutations at given sites in a DNA are well known, for example the M13 system. The DNA coding for the human receptor can be obtained by any known process; its sequence appears in annex 2.
In general, prokaryotes are used to clone the polypeptide sequences described above, for example E. coli 294 (ATCC No. 31446) is particularly useful. Other strains can be used, in particular E. coli X 1776 (ATCC No. 31537).
The polypeptides according to the present invention can be expressed in cells of bacteria, yeasts, mammals or other types of cells, under the control of an appropriate promoter, for example prokaryote systems such as for example E. coli can be used to express the recombinant proteins of the present invention. E. coli is typically transformed by using a derivative of pBR322 (ATCC 37017) which is a plasmid derived from a strain of E. coli (Bolivar et al, Gene 2, 95 (1977)). pBR322 contains genes for resistance to ampicillin and tetracycline and, also, provides simple means for identifying the transformed cells. The plasmid pBR322 or other microbe plasmids must also contain, or be modified so as to contain, sequences for expression control commonly used in recombinant DNA constructions.
Such control elements include for example the lactose (lac) promoter (J. Mol. Appl. Genet., 1, 139-147 (1981)) available under the No. ATCC 37121, the xcex2-lactamase promoter (Chang et al, Nature 275, 615 (1978)), the tryptophan promoter (Miozzari J. Bact. 133, 1457-1466 (1978) and hybrid promoters such as tac (H. de Boer et al, PNAS USA 80, 21-25 (1983)) available under the No. ATCC 37138. Other representative but non-limitative examples are commercial vectors such as for example pKK223-3 which contains the trc or pPL-lambda promoter which contains the phage lambda promoter and the thermolabile repressor c1857 (Pharmacia Fine Chemicals, Uppsala, Sweden).
Other functional promoters are suitable. The DNA sequences are generally known; thus they can be conjugated with a DNA coding for a variant of the soluble receptor of xcex1 and xcex2 interferons using appropriate binders or adapters. The promoters for the bacterial systems contain in addition a so-called Shine-Dalgarno (SD) sequence linked in an operative way to the DNA coding for the antigen downstream.
Also a subject of the present invention is expression vectors for producing useful quantities of variants of soluble receptor of purified xcex1 and xcex2 interferons.
After the transformation of a suitable host strain and the culture of the said host strain to a suitable culture density, the selected promoter is depressed by appropriate means (for example raising the temperature or chemical induction) and the micro-organisms are cultured again. The micro-organisms are typically collected by centrifuging, lysed by physical or chemical means and the extract is recovered for an additional purification.
The micro-organisms are fermented, for example in a 10-litre fermentor using maximum growth and aeration conditions and vigorous agitation. An anti-foam agent is preferably used. The cultures grow at 30xc2x0 C. in the super-induction medium as described by Mott et al, PNAS USA 82, 88 (1985), derepression is carried out at a culture density which corresponds to an A600 absorption of 5 to 6 by raising the temperature to 42xc2x0 C. and collection is carried out 2 to 20 hours, preferably 3 to 6 hours, after the temperature change. The mass of micro-organisms is firstly concentrated by filtration or by other means and then centrifuged at 10000 g for 10 minutes at 4xc2x0 C., then rapid congealing of the pellet is carried out. Recombinant proteins produced in bacterial culture are isolated by extraction of the pellet followed by one or more stages of concentration, desalting or ion-exchange or exclusion chromatography.
The micro-organisms used for the expression of variants of the soluble receptor of xcex1 and xcex2 interferons can be lysed by any suitable method, including congealing-decongealing cycles, sonication, mechanical rupture or the use of chemical agents. The soluble receptor of xcex1 and xcex2 interferons has a certain tendency to form aggregates which can be reduced by carrying out extraction and purification in the presence of a detergent such as Tween 80 or Triton X100.
For water-soluble polypeptides according to the present invention having a DNA sequence which does not start with methionine, the initiation signal will result in an additional methionine amino acid upstream and which represents the N-terminal residue of the product. Although such products having an additional N-terminal methionine can be used directly in the compositions and the methods of the present invention, it is normally preferable to remove this methionine beforehand. Standard methods in this field are known for removing such N-terminal methionines either in vivo or ex vitro.
Yeast systems, preferably using Saccharomyces types such as S. cerevisiae, commonly available, can also be used to express the polypeptides of the present invention.
In general, useful yeast vectors contain a replication origin and a selection marker allowing the transformation of the yeast as well as E. coli, for example the E. coli ampicillin resistance gene and the trpl gene of S. cerevisiae which provides a selection marker for a yeast mutant which cannot grow in tryptophan (available under ATCC No. 44076) and a promoter obtained from a gene superexpressed in the yeast to induce the transcription of a gene upstream. Appropriate promoter sequences for yeast hosts include the promoter of 3-phosphoglycerate kinase or other glycolysis enzymes, the promoter of acid phosphatase, for example PH05, the promoter of alpha type coupling factors. Other yeast promoters which can be used are promoter regions such as 2-alcoholdehydrogenase (Russell et al, J. Biol. Chem. 258, 2674, 1982). A signal peptide, for example the signal peptide of the factor allowing the secretion of a heterologous yeast protein can be inserted between the promoter and the structural gene to be expressed upstream (see Bitter et al, PNAS USA, 82, 5330, 1984). Yeast transformation methods are known to a man skilled in the art and a representative technique is described by Hinnen et al, PNAS USA 75, 1929 (1978) which permits trp+ transformants to be selected in a selection medium containing 0.67% nitrogenous yeast base, 0.5% Casamino acids, 2% glucose, 10 ug/ml uracil. Transformed host strains containing vectors having the PH05 promoter can be cultivated first in a preculture in a rich medium and subsequently depressed by reducing the concentration of inorganic phosphate in the medium. The strain is cultivated using conventional techniques.
The recombinant polypeptide is obtained by extraction of the cellular pellet which can be lysed either by enzymatic digestion with glucosidases followed by treatment with detergent or by mechanical forces such as for example the French press, followed by one or more stages of concentration, desalting, ion-exchange or exclusion chromatography. In the case where the polypeptide is secreted into the periplasmic space, it is recovered after treatment with chemical agents, for example EDTA which damages the outer layer of the membrane and which permits the release of the recombinant polypeptide. In the case where the polypeptide is secreted into the culture medium, it can be directly recovered.
Mammallian cells can also be used to express the polypeptides according to the present invention under the control of suitable promoters. Cell-free systems could also be used to produce soluble receptors of xcex1 and xcex2 interferons of mammals using RNAs derived from the DNA constructed by the present invention.
Promoters which control expression in mammalian host cells can be obtained from different sources, for example from virus genomes such as polyoma, simian Virus SV40, adenovirus, retrovirus, cytomegalovirus of hepatitis B or mammalian promoters, for example the promoter containing sites sensitive to DNAse I of the gene of human beta-globin or insect virus promoters such as the baculovirus system polyhedron promoter. For expression in animal cells, the control region derived from the late major promoter of adenovirus 2 is preferably used.
The early and late regions of SV40 are suitably isolated from the SV40 virus in the form of a restriction fragment which contains the replication origin of the virus (see Fiers et al, Nature 273, 113, 1978).
The early immediate region of the human cytomegalovirus is isolated in the form of a Hind IIIE restriction fragment (Greenaway P. J. et al, Gene 18, 3556360, 1982). The late promoter of the adenovirus-2 is isolated in the form of a Hind III restriction fragment containing the map units from 8 to 17 (S. Hu and J. L. Manley, Proc. Natl. Acad. Sciences (USA) 78, 820 to 824, 1981). Eukaryotic promoters of parent-type cellular origin are also useful.
In eukaryotic expression vectors, the transcription is increased by inserting, in addition to the promoter, sequences containing activators. The activators are DNA elements which act on the same side and which contain some 10 to 300 bp and increase the transcription initiation capacity of a promoter. Many of these activators are known for mammalian genes (globin, elastase, albumin, insulin, etc.). However, in general, activators of viruses infecting eukaryotic cells are used. Examples include the SV40 activator of the late side of the replication origin (100-270 bp), the activator of the early immediate promoter of cytomegalovirus, the activator of polyoma of the late side of the replication origin and the activator of adenovirus. The expression vectors used in the eukaryotic cells (yeasts, fungi, insects, plants, animal, human) can also contain sequences necessary for splicing and for termination of the transcription of factors which can influence the expression of mRNA. Expression vectors will contain a selection gene.
Examples of selection markers for mammalian cells are dehydrofolate reductase (DHFR), thymidine kinase or neomycin. When such selection markers are transfected into a host mammalian cell, the transformed cell can survive if it is put under selection pressure. In general, two types of selection systems are used. On the one hand, the use of a mutant line whose growth is dependent on a medium supplemented with certain ingredients such as for example CHO DHFR-cells or murine LTK-cells. These cells are not capable of growing without the addition of thymidine or hypoxanthine and these cells survive if a functional DHFR or TK gene is introduced by transfection. Thus, the cells not transformed by the DHFR or TK gene will not grow in the non-supplemented medium.
In addition, dominant selection is used which does not require a mutant cell: for example the gene which makes the transfected cell resistant to a toxic substance is transfected and expressed (see Southern and Berg, J. Molec. Appl. Genet. 1, 327 (1982); Mulligan and Berg Science, 20, 1422 (1980); Sugden et al, Mol. Cell. Biol. 5, 410-413 (1985).
The increase or the replication of certain chromosome regions of the cell is called amplification and can be brought about by using a selection agent such as for example methotrexate (MTX) which inactivates the DHFR. The amplification or increase of copies of the DHFR gene result in a greater production of DHFR with higher quantities of MTX. The degree of amplification increases with the concentration of MTX in the culture medium. The amplification of a desired gene is obtained by cotransfection of the desired gene and of the DHFR gene which are cointegrated in the chromosome. After co-amplification of the desired gene and the DHFR gene, the gene which codes for the desired protein expresses more of the desired protein.
The preferred host cells for the expression of variants of the soluble receptor of interferon of the present invention are mammalian cells which include monkey kidney cells (COS-7, ATCC CRL 1651 and Chinese hamster cells, CHO-DHFR-, Urlaub and Chasin, PNAS (USA), 77, 4216, 1980).
Transformation methods for mammalian cells are well known and a preferred method is described by Graham F. and van der Eb (Virology 52, 456-457, 1973) using the precipitation of DNA with calcium phosphate. Another method is electroportation as described by G. Chu et al, Nucl. Acid. Res. 15, 1311-1326, 1987. Other transfection methods such as for example injection into the nucleus or fusion with protoplasts can also be used.
The construction of expression vectors containing the desired control and coding sequences are prepared using well-known standard methods (see for example Maniatis T. et al, Molecular Cloning, 133-134 Cold Spring Harbor 1982; Current Protocols in Molecular Biology, edited by Ausubel et al, 1987, published by Greene Publishing Associates and Wiley-Interscience). The plasmids or fragments of DNA isolated are cut, sized and spliced again into the desired form.
The correct plasmid sequences are determined after transformation with ligation mixtures in E. coli HB101 or E. coli K12 294 (ATCC 31446). The transformants resistant to ampicillin are selected. The plasmids are isolated from the transformants and analyzed by restriction enzymes or by determination of the sequences by well-known methods (see Messing et al, Nucl. Acid Res. 9, 309 (1981) or Maxam et al, Methods in Enzymology 65, 499 (1980).
In general, the host cells are transformed by expression vectors, after which they are cultivated in an appropriate medium which contains substances for inducing the expression of the promoters, for selecting the transformants or for amplifying the genes. The culture conditions such as temperature, pH, etc. are those used for the selected culture for expression and are known to a man skilled in the art.
The polypeptides according to the present invention are isolated and purified from supernatants of recombinant host cells. Typically, the supernatants are concentrated by ultra-filtration, purified by ion-exchange chromatography or by immuno-affinity to adsorb the expected polypeptides and to subsequently elute them. The antigen has a great tendency to form aggregates. Thus, a detergent such as Tween 80, Triton X100 or CHAPS will advantageously be incorporated during purification. The final product will be stabilized with a protein such as albumin which may or may not contain a detergent.
It is however understood that all the vectors or sequences for controlling expression as well as all the host cells do not function in the same way for all the expression systems. However, a man skilled in the art will make a selection from these vectors, sequences for controlling expression and host cells, without moving outside the scope of the present invention. For example, single-cell hosts should be selected by considering their compatibility with the chosen vector, the toxicity of the product coded by the DNA sequences of the present invention, the secretion characteristics, their correct protein folding characteristics, their fermentation requirement and the ease of purification of the recombinant products after expression by the DNA sequences according to the present invention.
From these parameters, a man skilled in the art can select different vector system/expression control system/host cell combinations which express the DNA sequences according to the invention in fermentation or culture of animal cells on a large scale, for example CHO or COS-7 cells.
The polypeptides produced after expression of the DNA sequences according to the invention could be isolated from the fermentation or culture of animal cells and purified by a combination of conventional methods. A man skilled in the art will be able to select the most appropriate isolation and purification method without moving outside the scope of the present invention.
Also a subject of the present Application is cells, characterized in that they express a polypeptide described above and a preparation process for said polypeptides, characterized in that a cell capable of expressing the said polypeptide is cultivated in an appropriate nutritive medium.
The polypeptides according to the present invention are useful in particular as immunomodulators, quite particularly immuno-suppressants, and can be used in the treatment of auto-immune illnesses and graft rejections.
That is why a subject of the present Application is also medicaments, characterized in that they are constituted by water-soluble polypeptides as defined above.
Also a subject of the present Application is pharmaceutical compositions, characterized in that they contain as active ingredient one of the medicaments as defined above.
The purified polypeptides can be formulated in a pharmacologically acceptable conventional form. The constituents of this invention contain an immuno-therapeutically effective quantity of a polypeptide according to the present invention and a pharmaceutically acceptable support. The constituents according to the present invention can be presented in various forms: solid, semi-solid and liquid, in the form of tablets, pills, powder, injectable or infusable solutions. The preferred form depends on the administration method and the therapeutic use. In general, the pharmaceutical composition of the present invention will be administered using methods and compositions similar to those employed for other pharmaceutically important polypeptides. Thus, the polypeptide can be preserved in lyophilized form, reconstituted with sterilized water just before administration and administered by the usual routes, that it to say parenteral, sub-cutaneous, intravenous, intramuscular or intralesional. An effective dose may be of the order of 1 to 5 mg/kg of body weight/day. It is understood that a weaker or stronger dose exceeding twice the higher dose can be injected without harmful effects.
The medicaments according to the invention can be administered to patients in whom the abnormal production of xcex1 and xcex2 interferons is harmful, for example in illnesses such as lupus erythematosus, Behcet""s syndrome, aplastic anaemia, diabetes mellitus, multiple sclerosis, rheumatoid arthritis or serious immuno-deficiency illnesses or to patients suffering from AIDS. Furthermore, the constituents according to the present invention, due to their ability to modify the immune activities such as activation of NK cells or expression of histocompatibility antigens, will also be administered as a therapeutic treatment to patients suffering from the rejection of organ grafts.
Due to their nature and their action mechanism, the compositions according to the present invention are free from general toxicity such as that of chemical immuno-suppressants such as glucocorticoids and therefore represent a great improvement relative to the medicaments in clinical use at present: for example immuno-suppressant substances or derivatives of such substances such as adrenal corticosteroids which inhibit cell division and the synthesis of cytokins for all the elements of the immune system or such as cyclosporin, a cyclic undecapeptide which selectively inhibits the activation of the immune system and represents an obvious improvement but which has a large number of non-immunological toxic effects (see N. Engl. J. Med., 321:25, 1725-1738, 1989).
The constituents according to the present invention can also be used to control agonists or antagonists which are different from xcex1 and xcex2 interferons.
The constituents according to the present invention in purified form are also useful for determining the tertiary structure of the fixation site of the soluble receptor of xcex1 and xcex2 interferons, a pre-condition for producing the molecular design in order to deduce from it the structures serving as a model for the synthesis of antagonists therapeutically useful as an immuno-suppressant agent or agonists useful as an anti-viral and anti-tumour agent.
Finally a subject of the present Application is therefore the use of a polypeptide as defined above, as a diagnostic agent, as well as the preparation of anti-xcex1 or xcex2 interferon antibodies.
The following examples illustrate the present invention without however limiting it.